Programmable current source

[johnkaz77]

Hi everyone,I want to make a programmable current source (or current sink,depending on a digital signal) to provide me 0 to 10uA,10 bits resolution,but i am a beginner and i don't have a clue...Can anyone help???

 

[Prototyp_V1.0]

A solution is to build/buy a propriate DAC and then connect it to a opamp current sink/source circuit. Like the one below:

 

[johnkaz77]

Could you explain that a little bit more?I guess my output will be from the unconnected wire,but how can i select if it will be sourcing or sinking?I want an external digital signal to control that.And the transistor,why is it used for?(as i told you i am beginner...)

 

[Prototyp_V1.0]

Could you explain that a little bit more?I guess my output will be from the unconnected wire,but how can i select if it will be sourcing or sinking?I want an external digital signal to control that.And the transistor,why is it used for?(as i told you i am beginner...)

HI. I would have tried to solve this using a current source with two outouts. Then one output should be connected to an inverted current mirror (two pnp instead of two npn bjt's) wich in turn will provide output from current source.
You would need two similar circuits of the one I drawed for you in my last post (I don't know any ways to simplify).

Also you must provide one bjt for both current source and current sink (the current mirror circuit) to control their on and off state - because that's how to switch between current source/sink.